Overview

We're spending today going through Test 4 Retake

Notes

Had trouble with

  • Conservation of momentum
    • How to set it up
  • Needs help with setting up problems
  • Past couple sessions have been helpful, but they're things he's more strong with
    Next couple weeks, homework is computationally lighter, but should be practicing.
  • Each class Humza preps and teaches the questions
    Midterm is 1.5-2hrs
    3 months from the AP now, good time to start thinking about that.
  • 12 sessions left till the AP, we're likely not clearing all the material
Exercise (Puck A (0.6 kg) moves at 5.0 m/s along the +x-axis. Puck B (0.4 kg) moves at 4.0 m/s at 30° below the +x-axis. They collide elastically on a frictionless surface.

(a) Write the conservation of momentum equations in the x- and y-directions. (4 pts)
(b) State why kinetic energy is conserved. (1 pt)
(c) Solve for the final velocity components of both pucks. (5 pts) ).

test

Notes on how he worked through it:

  • Good that he drew it out first thing, but it seems like his drawing is wrong
  • Both pucks move along the positive , and collide in the same direction.
  • Good that he used soh-cah-toah so fast! I like that he put the triangles right on-top.
  • I didn't notice any drawings on the test originally, so he teaches differently to how he learns.
  • When he started teaching, he looked at the wrong problem from a previous test which was the same concept. Once he noticed he was on the wrong problem, he said he didn't know how to do it even though he was explaining it moments before. I think the problems are intimidating him

After correcting him, his diagram looks good!
Correctly identified the components.

Correctly identified overall momentum equation on his own
He's starting to make small technical mistakes that aren't characteristic of him. Multiplying momentum together instead of adding, putting cosine on the wrong terms, those are things that suggest we need to review the basics again. You don't make mistakes like that if you understand a concept, you make them from memorizing.
Needed me to get him rolling with kinetic energy, we should also review elastic collisions.

  • This will need a full lesson next time
Exercise.

A stationary 2.0 kg firework explodes into two fragments:

  • Fragment 1 (1.2 kg) flies northeast at 6.0 m/s.
  • Fragment 2 (0.8 kg) flies southwest.

(a) Calculate Fragment 2’s velocity (magnitude and direction). (5 pts)
(b) Determine if kinetic energy is conserved in the explosion. Show work. (3 pts)

  • Needed me to talk through the setup here
  • Once I gave him a hint, he felt more confident about the question and could do it himself
    I think this unit is also psyching him out
Homework Total length ~ [60-70min]

Febuary 25th whole unit midterm to cover material

  1. Redo MCQ section on first Test 4. Show your work, be prepared to talk through 3 at random during class
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